Question

A and b can complete a piece of work in 10 days and 15 days respectively.B starts the work and os joined by a after 5 days

Answer 1

$a =10days \\ b = 15days \\os = 5days \\ b + os = 15 - 5 = 10days \\ they \: will \: complete \: their \: work \: in \:20 days$